1. Field of the Invention
The present invention relates to a two-dimensional position detecting apparatus for ink drops in an ink jet system recording apparatus.
2. Description of the Prior Art
In an ink jet system recording apparatus of the multi-nozzle type, as shown in FIG. 3, it is necessary to perform such a switching operation that the respective ends of printing regions 13 and 14 assigned by nozzles (in the drawings, an example provided with two nozzles 11 and 12 is shown) are made to agree with each other at a boundary or stitching point 15 between the regions 13 and 14 on a surface of paper 10. If this stitching operation is not performed in the optimum manner, overlapped printing or blank portions may be produced. Therefore, in the ink jet system recording apparatus of the multi-nozzle type, the position of an ink drop 16 to be printed by an ink drop 16 at the stitching point 15 is detected by an ink-drop position detector or an ink-drop sensor to thereby perform position control of the ink drops 16.
As the conventional position detecting sensor, there have been proposed such sensors as are disclosed, for example, in Japanese Patent Application (OPI) Nos. 118870/1980 and 125408/1980 (the term "OPI" as used herein means an "unexamined published application"). A brief description will be given as to the arrangement of the sensor disclosed in Japanese Patent Application (OPI) No. 125408/1980. In this sensor, an ink-drop detecting region is defined in a space between one end surface of an input fiber and respective one end surfaces of two output fibers for each of the detecting sites, and an LED light source is connected to the other end of the input fiber while two photosensors are connected to the other ends of the output fibers, respectively.
In this arrangement, when an ink drop comes in a region between the input and output fibers, respective outputs of the two photosensors vary with the lapse of time, so that the passing of an ink drop through the detecting site is indicated by a detecting circuit connected to the photosensors.
In the conventional position detecting apparatus for ink drops, however, it is required to provide a detecting unit constituted by a light source and a pair of detectors or photosensors in order to detect a linear or one-dimensional position of an ink drop, and therefore it is necessary to provide two sets of the same detecting units in order to detect a two-dimensional position of an ink drop, the two-dimensional position detection being required for performing high-quality printing. Consequently, there have been such disadvantages that the number of parts of the position detecting apparatus is necessarily increased, and that it is difficult to set the position detecting apparatus in a narrow space and to define the paths for the position detection.